This application requests financial support for the Third International Conference on the Properties and Functions of Na,K-ATPase which is to be held August 17-21, 1981 at Yale University in New Haven, CT. The 4-1/2 day meeting will be attended by approximately 50 foreign and 100 U.S. scientists, the majority of whom will make oral or poster presentations of original work. The first two conferences in this series were held in 1973 and 1978; there have been no other meetings devoted primarily to Na,K-ATPase. Na,K-ATPase is the enzyme in the plasma membrane of most animal cells that is responsible for coupling the hydrolysis of ATP to the outward transport of Na and inward movement of K across the membrane against electrochemical gradients. The maintenance by this process of high K+ and low Na+ inside the cell is of fundamental importance in control of cell volume, and in the electrical excitability of nerve and muscle. The Na gradient established by Na,K-ATPase is used by coupled transport systems to drive the cellular accumulation of solutes such as sugars and amino acids and extrusion of others such as Ca++ and protons. In epithelia the net movement of salt, water and other solutes across the tissue results. In heart, through changes in intracellular Ca++ coupled to the Na+ gradient, the Na,K-ATPase is believed to be the site of the positive ionotropic action of cardiac glycosides in enhancement of cardiac contractility. The proposed conference will address all aspects of current work on the properties and functions of Na,K-ATPase. Sessions will be devoted to structure, kinetics and molecular mechanism of the purified enzyme and to transport in intact membrane systems, to in vivo synthesis and regulation of the Na-K pump, and to its role in health and disease.